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Hawaiian Islands Synoptic Discussion and Guidance

395
FXHW60 PHFO 271330
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST FRI MAR 27 2015

.SYNOPSIS...
A DRY AND STABLE AIRMASS HAS SETTLED ACROSS THE MAIN HAWAIIAN
ISLANDS...LIMITING RAINFALL WITHIN CONTINUED BREEZY EASTERLY TRADE
FLOW. TRADE WINDS WILL GRADUALLY DECLINE TODAY AND SATURDAY AS LIGHT
SHOWERS REMAIN CONFINED TO WINDWARD SLOPES. TRADE WIND FLOW MAY BE
BRIEFLY DISRUPTED ON TUESDAY AS AN AREA OF DISTURBED WEATHER PASSES
NEAR OR JUST NORTH OF THE STATE.

&&

.DISCUSSION...
THE OLD FRONTAL BAND HAS COMPLETELY DISSIPATED...LEAVING STABLE AND
RATHER DRY CONDITIONS ACROSS THE MAIN HAWAIIAN ISLANDS THIS MORNING.
OVERNIGHT SOUNDINGS SHOW STRONG SUBSIDENCE INVERSIONS...POSITIVE
LIFTED INDEX VALUES AND CAPE LESS THAN 200 J/KG WHILE PW REMAINS
LESS THAN AN INCH AT LIHUE AND AROUND 1.2 INCHES AT HILO. RADAR
SHOWS ISOLATED LIGHT SHOWERS EMBEDDED WITHIN EAST NORTHEAST TRADE
FLOW AFFECTING WINDWARD AREAS OF THE ISLANDS. RIDGING ALOFT WILL
MAINTAIN STABLE CONDITIONS...AND WITH SUCH LOW PW VALUES WE DO NOT
EXPECT SIGNIFICANT RAINFALL.

LOCALLY BREEZY AND GUSTY TRADES WILL GRADUALLY DIMINISH TODAY AND
SATURDAY AS A 1030 MB HIGH PASSING NORTH OF THE ISLANDS ALONG 30N
MOVES OFF TO THE EAST. TRADES SHOULD BRIEFLY INCREASE A NOTCH ON
SUNDAY AS ANOTHER HIGH PASSES WELL NORTH OF THE STATE.

RATHER DRY TRADE WIND WEATHER IS EXPECTED INTO THE WEEKEND. EXPECT
LIMITED WINDWARD SHOWER ACTIVITY ALONG WITH RATHER DRY LEEWARD
CONDITIONS. THE TRADE WIND FLOW COULD BE DISRUPTED AROUND TUESDAY.
MODELS SHOW A FRONT STALLING A COUPLE HUNDRED MILES NORTH OF THE
ISLANDS ON SUNDAY. MODELS ALSO SHOW AN UPPER LEVEL TROUGH PASSING
OVER OR JUST NORTH OF THE STATE SOMETIME MONDAY NIGHT THROUGH
TUESDAY NIGHT. THIS FEATURE COULD BE STRONG ENOUGH TO TAP MOISTURE
ALONG THE FRONT...DISRUPTING THE TRADES AND POSSIBLY LEADING TO
INCREASED SHOWER ACTIVITY OVER THE NORTHERN ISLANDS.

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL OVER LEEWARD AREAS WITH TEMPO MVFR
CEILINGS OVER WINDWARD AREAS THROUGH THE MORNING. AIRMET SIERRA IS
IN EFFECT FOR MTN OBSC OVER NE SECTIONS OF KAUAI. THESE CONDITIONS
WILL LIKELY CONTINUE THROUGH EARLY MORNING. VFR CONDITIONS SHOULD
PREVAIL AREA-WIDE BY 28/0000Z. STRONG TRADE WINDS AND A STRONG LOW
LEVEL TEMPERATURE INVERSION WILL COMBINE TO PRODUCE LOW LEVEL
TURBULENCE. AIRMET TANGO IS IN EFFECT FOR TURB S THRU W OF THE MTN
OF ALL ISLANDS.

&&

.MARINE...
AN OVERNIGHT SCATTEROMETER PASS ACROSS THE ISLANDS REVEALED THAT
SMALL CRAFT ADVISORY THRESHOLD WINDS WERE OCCURRING ACROSS CHANNELS
WEST OF THE ADVISORY AREA. THE SMALL CRAFT ADVISORY HAS THEREFORE
BEEN EXPANDED TO INCLUDE KAUAI NORTHWEST WATERS AS WELL AS THE KAUAI
AND KAIWI CHANNELS THROUGH THIS AFTERNOON. THE SMALL CRAFT ADVISORY
ALSO COVERS THE WINDIER WATERS ACROSS THE EASTERN HALF OF THE
STATE. TRADE WINDS WILL BE ON A GRADUAL DECLINE TODAY AND SATURDAY.

SEAS ARE ELEVATED DUE TO A MIX OF LARGE WIND WAVES...A DECLINING
NORTH-NORTHWEST SWELL AND A DECLINING SOUTH-SOUTHWEST SWELL. THE
DECLINING NORTH-NORTHWEST SWELL WILL BE FOLLOWED BY ANOTHER MODERATE
NORTHWEST SWELL THIS WEEKEND. THE SOUTH-SOUTHWEST SWELL WILL
CONTINUE TO FADE TODAY...GIVING WAY TO A SMALL TO MODERATE
SOUTH-SOUTHEAST SWELL TODAY INTO EARLY NEXT WEEK. NO HIGH SURF
ADVISORIES ARE ANTICIPATED AT THIS TIME.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 PM HST TODAY FOR NORTHWEST KAUAI
WATERS-KAUAI CHANNEL-KAIWI CHANNEL-MAALAEA BAY-PAILOLO
CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND
SOUTHEAST WATERS.

&&

$$

DISCUSSION/MARINE...POWELL
AVIATION...DONALDSON





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